Studies are currently in progress to determine whether or not fast neutron therapy is more effective than conventional forms of treatment in controlling locally advanced malignant tumors. Controlled clinical trials have been initiated by the Middle Atlantic Neutron Therapy Association for squamous cell carcinomas of the upper aerodigestive tract and for glioblastoma multiforme tumors. Similar trials for the treatment of locally advanced tumors of the uterine cervix, urinary bladder and prostate are to be initiated. Pilot studies for the treatment of carcinoma of the esophagus, carcinoma of the pancreas, chondrosarcomas and other locally advanced tumors are also in progress.